Maybe only a really, really rich guy can credibly make the case for why the wealthy should be asked to pay more in taxes. You can’t accuse a big capitalist of “class warfare.” That’s why the right wing despises Warren Buffett and is trying so hard to shut him up.

Militant conservatives are effective because they are absolutely shameless. Many of the same people who think the rich should be free to spend unlimited sums influencing our politics without having to disclose anything are now asking Buffett to make his tax returns public. I guess if you’re indifferent to consistency, you have a lot of freedom of action.

Buffett has outraged conservatives by saying that he pays taxes at a lower rate than his secretary. He’s said this for years, but he’s a target now because President Obama is using his comment to make the case for higher taxes on millionaires.

Thus did the Wall Street Journal editorial page call on Buffett to “let everyone else in on his secrets of tax avoidance by releasing his tax returns.”

Somehow, the Journal did not think to ask its friends who battle vigorously for low taxes on capital gains to release their tax returns, too. But aren’t they just as engaged in this argument as Buffett? Shouldn’t accountability go both ways? Nor did the Journal suggest that the Koch brothers could serve the public interest by releasing a full accounting of all their political spending.

Buffett’s sin is that he spoke a truth that conservatives want to keep covered up: Taxing capital gains at 15 percent means that people who make their money from investments pay taxes at a much lower marginal rate than those who earn more than $34,500 a year from their labor. That’s when the income tax rate goes up to 25 percent. (For joint filers, the 25 percent rate kicks in at $69,000.) For singles, the 28 percent bracket starts at $83,600, the 33 percent bracket at $174,400.

So if an investor such as Buffett pockets, say, $100 million of his income in capital gains, he pays only a 15 percent tax on all that money. For everyday working people, the 15 percent rate applies only to earnings between $8,500 and $34,500. After that, they’re paying a higher marginal rate than the multimillionaire pays on gains from investments. Oh, yes, and before Obama temporarily cut it by two points, the payroll tax added another 6.2 percent to the burden on middle-class workers. That levy doesn’t apply to capital gains or to income above $106,800, so it hits low- and middle-income workers much harder than it does the wealthy.

No wonder partisans of low taxes on wealthy investors hate Warren Buffett. He has forced a national conversation on (1) the bias of the tax system against labor; (2) the fact that, in comparison with middle- or upper-middle-class people, the really wealthy pay a remarkably low percentage of their income in taxes; and (3) the deeply regressive nature of the payroll tax.

(Because this column appears in The Post, I should note that Buffett heads a company that owns a substantial minority share in The Washington Post Co. and for many years held a seat on the company’s board of directors.)

It’s worth noticing that while conservatives who talk about religion get a lot of coverage — and I will always defend their freedom to speak of faith in the public square — what really get the juices flowing on the right these days are tax rates. I’m not sure that a politician who renounced the Almighty would get nearly the attention Buffett has received for his renunciation of low capital gains taxes.

Advocates of higher taxes on the wealthy do not want to “punish” the successful. Buffett and Doug Edwards, a millionaire who asked Obama at a recent town hall event in California to raise his taxes, are saying that none of us succeeds solely because of personal effort. We are all lucky to have been born in — or, for immigrants, admitted to — a country where the rule of law is strong, where property is safe, where a vast infrastructure has been built over generations, where our colleges and universities are the envy of the world, and where government protects our liberties.

Wealthy people, by definition, have done better within this system than other people have. They ought to be willing to join Buffett and Edwards in arguing that for this reason alone, it is common sense, not class jealousy, to ask the most fortunate to pay taxes at higher tax rates than other people do. It is for this heresy that Buffett is being harassed.